Opposed piston power unit

ABSTRACT

A piston power unit primarily for use as an internal combustion engine and having a single cylinder curved about a center, intake and exhaust ports at opposite ends of the cylinder, a pair of opposed pistons movable in the cylinder towards and away from each other in compression and power strokes, said pistons covering these ports during most of their strokes and successively opening the ports as the pistons approach the ends of their respective power strokes, a pair of crank shafts including intermeshing gears, and a pair of connecting rods connecting the crankshafts to the pistons. The pistons are oscillated so that one opens the exhaust port a little before the other piston opens the intake port, and the pistons close the two ports at substantially the same time. This can be accomplished by locating the journal of the connecting rod of one piston closer to the centre of arc of the cylinder than that of the other piston, or by making the throw of one crankshaft greater than that of the other crankshaft, or by advancing the throw of one crankshaft ahead of the throw of the other crankshaft.

[ 51 Oct. 7, 1975 OPPOSED PISTON POWER UNIT [76] Inventor:

[57] ABSTRACT A piston power unit primarily for use as an internal Richard James, 5025 Granville St., Vancouver, British Columbia, Canada combustion engine and having a single cylinder curved about a center, intake and exhaust ports at opposite ends of the cylinder, a pair of opposed pistons mov- 22 Filed: June 10, 1974 A N 47 173 able in the cylinder towards and away from each other in compression and power strokes, said pistons covering these ports during most of their strokes and suc- [52] US. 123/18 R F02B 53/00; F02B 55/00 cessively opening the ports as the pistons approach the Int.

[51] ends of their respective power strokes, a pair of crank Fleld 0f R, A h f including intermeshing g and a p of necting rods connecting the crankshafts to the pistons.

[56] References Cited UNITED STATES PATENTS 3,338,137 8/1967 3,388,693 6/1968 James"... FOREIGN PATENTS OR APPLICATIONS ton closer to the centre of arc of the cylinder than that of the other piston, or by making the throw of one 123/18 A 123/18 A 123/18 R crankshaft greater than that of the other crankshaft,

25,945 1912 United Kingdom............... 856,619 12/1960 United Kingdom..... 53,580 12/1942 Netherlands...,..................

or by advancing the throw of one crankshaft ahead of Primary Examiner-wendeu E Bums the throw of the other crankshaft.

Attorney, Agent, or Firm-Fetherstonhaugh & Co. 9 Claims, 3 Drawing Figures US. Patent Oct. 7,1975 Sheet 1 of2 3,910,239

3 W 3 4 "A r I Q OI US. Patent Oct. 7,1975 Sheet 2 Of2 3,910,239

OPPOSED PISTON POWER UNIT The invention relates to opposed piston power units and in particular to a modification in the piston power unit of US. Pat. No. 3,338,137.

The piston power unit disclosed in the above numbered patent has a single cylinder curved about a centre and having inlet and exhaust ports at opposite ends, and in which a pair of opposed pistons are movable. The pistons are connected through connecting rods to two different cranks of a single crankshaft, said cranks being phased so as to cause the exhaust port to be uncovered in advance of the inlet port and for both ports to be covered substantially simultaneously. This arrangement allows for a blowdown period before the intake port is opened, and the closing of the ports at substantially the same time reduces or eliminates the loss of new charge fuel from the intake port through the exhaust port. An engine which displays these characteristics is said to have assymetrical port timing.

However, the use of a double throw single crankshaft although satisfactory in operation, leads to expensive complications in construction of the engine. Due to the inevitable offset of the connecting rods axially of the crankshaft, the pistons must have complementary offset portions and journals. This leads in turn to a necessity for complex machining both of the pistons and of the cylinder. In addition, it is difficult to seal the pressure in the cylinder, and the offset disturbs the scaveng ing air flow, thereby creating a turbulence which causes some of the new charge to mix with the exhaust gases. This prevents complete scavenging of the gases, leaving a contaminated charge in the cylinder.

It is among the objects of the present invention to provide a simplified form of opposed piston power unit of the same general type as disclosed in the above numbered United States patent but eliminating the stated problems and which still achieves assymetrical port timing with the desirable characteristics associated therewith. Another advantage of the present power unit is reduced vibration.

The invention therefore provides a piston power unit comprising a cylinder curved longitudinally about a center and formed with exhaust and intake ports respectively adjacent its first and second ends thereof, first and second opposed pistons slidably fitting in said cylinder for movement towards and away from each other in compression and power strokes respectively, and so as to uncover said exhaust and intake ports respectively during their power strokes, each piston having a head at one end facing the opposed piston and journal means at the other end for journalling the end of a connecting rod, means connected to the other end of each piston constraining said piston to move about said centre when the pistons oscillate in the cylinder, first and second crankshafts for the first and second pistons and each having a crank, means operatively interconnecting said crankshafts for rotation at the same speed and in phase, and first and second connecting rods each journalled at one end to the crank of the respective crankshaft and at the other end to the journal means of the respecitve piston, said piston journal means and said cranks being arranged so that the first piston uncovers the exhaust port before the second piston uncovers the intake port.

In a preferred form of the invention, the axis of the journal means for the first piston is closer to said center of the cylinder than the axis of the journal means for the second piston. Alternatively, the throw of the crank of the first piston can be greater than the throw of the crank of the second piston.

Two embodiments of the invention will now be described with reference to the accompanying drawings in which,

FIG. 1 is a sectional elevation of the preferred embodiment of the invention,

FIG. 2 is a sectional elevation of an alternative embodiment of the invention, and

FIG. 3 is a fragmentary sectional elevation illustrating another alternative embodiment of the invention.

Since the embodiments of FIGS. 1 and 2 are closely related structurally, the initial part of the following description relates to both Figures, the features which differ being subsequently described.

Referring to the drawings, FIGS. 1 and 2 show piston power units 1 and 2 respectively each in the form of an internal combustion engine. Each unit is generally circular in form and has a casing 3 including a generally circular upper lobe 4 and an elongated lower lobe 5. The ends of the casing are closed by opposed side walls 6, only one of which is shown in the drawings.

The upper lobe 4 of the casing is formed by a wall 7 in which cavities 8 are formed for the passage of a coolant such as water. The inner wall of the wall 7 is formed with a circular inner surface 9 which curves around a fulcrum shaft 10 located centrally and extending transversely of the casing 3. The ends of the shaft are rotatably supported by the walls 6 in a conventional manner (not shown).

A curved inner wall 11 is spaced inwardly from the inner surface 9 of the wall 7 and is concentric therewith and with the shaft 10. Inner wall 11, the wall surface 9 and the end walls 6 form a cylinder 12 which is curved longitudinally about the center or longitudinal axis of shaft 10. In this example, the cylinder 12 is rectangular in cross-section, but it is to be understood that it may have any desired cross-sectional shape, for example it may be circular or elliptical. At one end of the cylinder 12, an intake port 13 is formed in the wall 7, whilst at the other end, an exhaust port 14 extends through the wall 7.

Opposed longitudinally curved pistons 15 and 16 of the same cross-sectional shape as the cylinder 12 are slidably mounted in the cylinder for movement towards and away from each other in compression and power strokes, respectively. The pistons 15 and 16 have heads 17 and 18 at adjacent ends thereof and facing each other. At the ends of the pistons remote from the heads 17 and 18, arms 19 and 20 are fixedly secured thereto. The arms 19 and 20 project inwardly and are journalled on shaft 10, a suitable low friction bearing 21 being provided for each arm.

Pistons 15 and 16 are adapted to oscillate in the cylinder 12, and as the cylinder is concentric with the shaft 10, the pistons oscillate around the longitudinal centre or axis of the shaft. As the arms 19 and 20 are fixedly secured to pistons 15 and 16 and are rotatably connected to the shaft 10, the arms constrain the pistons to move along circular paths about the centre of the shaft 10 so that there is no side thrust against the walls of the cylinder. The pistons 15 and 16 are provided with one or more piston rings adjacent their respective heads in a conventional manner. The lower lobe of the casing 3 constitutes a crank case having a pair of crankshafts 22 and 23 therein, the crankshafts being journalled in journals (not shown) in the end walls 6. One of the crankshafts extends through an end wall to provide a drive. Within the crank case, the

crankshafts 22 and 23 carry gears 24 and 25 of the same size which mesh at 26. The gears and crankshafts are thus constrained to rotate at the same speed in op posite directions. Cranks 27 and 28 of the crankshafts 22 and 23 are connected respectively to the pistons 15 and 16 by connecting rods 29 and 30. The upper ends of the connecting rods 29 and 30 are journalled or wrist pins 31 and 32 of pistons 15 and 16, respectively.

The crank case has an inlet connection 33 for a combustion mixture. The mixture within the crank case is transferred to the cylinder 12 during each down-stroke of the pistons through a transfer passage 34 in wall '7 which extends from the crank case to intake port 13. However, it will be appreciated that if fuel injection techniques are used, air alone will be introduced through the intake 33. Alternatively, the intake port 13 may extend directly through the wall 7 from a carburetor and supercharger combination. Such alternatives are well known in the art and will not be described further. For a gasoline engine, a spark plug 35 will be provided in wall 7 substantially midway between the ends of cylinder 12, as shown, but it will be evident that in case of a compression ignition engine the plug will be omitted.

Referring now specifically to the embodiment of FIG. 1, the axis of the wrist pin 32 is set closer to the axis of the shaft than the axis of the wrist pin 31, the spacing between axes of movement of the wrist pins being indicated at 36. At the same time, the cranks 27 and 28 are set in phase in their opposed directions of rotation.

With the arrangements shown in FIG. 1, the piston 16 will move downwardly during the power stroke at a greater rate than the piston 15, thus uncovering the exhaust port 14 before piston uncovers intake port 13. A blowdown period will thus be provided for the scavenging of the cylinder before the intake port opens. At the same time, due to the fact that the two halves of the engine, each comprised by a piston, connecting rod and crankshaft, are in dynamic balance, vibration in the engine will be reduced to a minimum. Furthermore, pistons l5 and 16 close the intake and exhaust ports at substantially the same time.

Turning now the embodiment of FIG. 2, it will be seen that crank 28 of the crankshaft 23 is advanced in phase by an angle 37 relative to crank 27 of crankshaft 23. In this case however the axes of the wrist pins 31 and 32 are equally spaced from the axis of the shaft 10. The phasing of the crankshafts in this case achieves the earlier opening of the exhaust port 14. It will be appreciated that the angle 37 has been exaggerated in FIG. 2 in order to illustrate the principle involved. In practice, the angle 37 is in the region of 3.

In the embodiment of FIG. 3, the desired movement of piston 16 is attained by making the throw of crank 28 greater than the throw of crank 27. This difference is indicated in exaggerated form by lines 40 and 41, line 40 being longer than line 41. This arrangement causes piston 16 to travel further than piston 15 during each stroke so that piston 16 covers and uncovers exhaust port 14 before piston 15 respectively covers and uncovers intake port 13. The axes of wrist pins 31 and 32 are equally spaced from the axis of shaft 10, as in FIG. 2.

As there are two crankshafts rotating in opposite directions, there is less vibration created than there would be in a single crankshaft engine of this type. As each connecting rod is substantially moving up and down, there is comparatively little bending movement where each piston is attached to its connecting arm. In addition, it is comparatively easy to balance this engine, since each crankshaft balances only the piston to which it is connected.

I claim.

1. A piston power unit, comprising a cylinder curved longitudinally about a centre and formed with exhaust and intake ports respectively adjacent first and second ends thereof,

first and second opposed pistons slidably fitting in said cylinder for movement towards and away from each other in compression and power strokes respectively, and so as to uncover said exhaust and intake ports respectively during their power strokes, each piston having a head at one end facing the opposed piston and journal means at the other end for journalling the end of a connecting rod,

means connected to the other end of each piston constraining said piston to move about said centre when the pistons reciprocate in the cylinder,

first and second crankshafts for the first and second pistons and each having a crank, means operatively interconnecting said crank-shafts for rotation at the same speed and in phase, and

first and second connecting rods each journalled at one end to the crank of the respective crankshaft and at the other end to the journal means of the respective piston,

said piston journal means and said cranks being arranged so that the first piston uncovers the exhaust port before the second piston uncovers the intake port.

2. A piston power unit as claimed in claim 1, wherein said piston journal means and said cranks are arranged so that the first piston starts to uncover the exhaust port before the second piston starts to uncover the intake port during the power strokes of the pistons, the pistons covering said ports at substantially the same time during the compression strokes of the pistons.

3. A piston power unit as claimed in claim 1, wherein the means operatively interconnecting said first and second crankshafts comprises intermeshing gears.

4. A piston unit as claimed in claim 1, wherein said means operatively interconnecting said first and second crankshafts constrain said crankshafts to rotate in opposite directions.

5. A piston power unit as claimed in claim 1, wherein the journal means of the first piston is closer to said center than the journal means of the second piston.

6.- A piston power unit as claimed in claim 1, wherein the throw of the crank of the first piston is greater than the throw of the crank of the second piston.

7. A piston power unit, comprising a cylinder curved longitudinally about a centre and formed with exhaust and intake ports respectively adjacent first and second ends thereof,

first and second opposed piston slidably fitting in said cylinder for movement towards and away from each other in compression and power strokes respectively, and so as to uncover said exhaust and intake ports respectively during their power 6 strokes, each piston having a head at one end facvance of the crank of the second crankshaft, and ing the opposed piston and journal means at the first and second connecting rods each journalled at other end for journalling the end of a connecting one end to the crank of the respective crankshaft rod with the axes of the journal means for said pisand at the other end to the journal means of the retons being equally spaced from said centre, 5 spective piston. means connected to the other end of each piston con- 8. A piston power unit as claimed in claim 7, wherein straining said piston to move about said centre the means operatively interconnecting said first and when the pistons reciprocate in the cylinder, second crankshafts comprises intermeshing gears. first and second crankshafts for the first and second 9. A piston power unit as claimed in claim 7, wherein pistons and each having a crank, 10 said means operatively interconnecting said first and means operatively interconnecting said crankshafts second crankshafts constrain said crankshafts to rotate for rotation at the same speed, with the throw of in opposite directions. the crank of the first crankshaft being phased in ad- 

1. A piston power unit, comprising a cylinder curved longitudinally about a centre and formed with exhaust and intake ports respectively adjacent first and second ends thereof, first and second opposed pistons slidably fitting in said cylinder for movement towards and away from each other in compression and power strokes respectively, and so as to uncover said exhaust and intake ports respectively during their power strokes, each piston having a head at one end facing the opposed piston and journal means at the other end for journalling the end of a connecting rod, means connected to the other end of each piston constraining said piston to move about said centre when the pistons reciprocate in the cylinder, first and second crankshafts for the first and second pistons and each having a crank, means operatively interconnecting said crank-shafts for rotation at the same speed and in phase, and first and second connecting rods each journalled at one end to the crank of the respective crankshaft and at the other end to the journal means of the respective piston, said piston journal means and said cranks being arranged so that the first piston uncovers the exhaust port before the second piston uncovers the intake port.
 2. A piston power unit as claimed in claim 1, wherein said piston journal means and said cranks are arranged so that the first piston starts to uncover the exhaust port before the second piston starts to uncover the intake port during the power strokes of the pistons, the pistons covering said ports at substantially the same time during the compression strokes of the pistons.
 3. A piston power unit as claimed in claim 1, wherein the means operatively interconnecting said first and second crankshafts comprises intermeshing gears.
 4. A piston unit as claimed in claim 1, wherein said means operatively interconnecting said first and second crankshafts constrain said crankshafts to rotate in opposite directions.
 5. A piston power unit as claimed in claim 1, wherein the journal means of the first piston is closer to said center than the journal means of the second piston.
 6. A piston power unit as claimed in claim 1, wherein the throw of the crank of the first piston is greater than the throw of the crank of the second piston.
 7. A piston power unit, comprising a cylinder curved longitudinally about a centre and formed with exhaust and intake ports respectively adjacent first and second ends thereof, first and second opposed piston slidably fitting in said cylinder for movement towards and away from each other in compression and power strokes respectively, and so as to uncover said exhaust and intake ports respectively during their power strokes, each piston having a head at one end facing the opposed piston and journal means at the other end for journalling the end of a connecting rod with the axes of the journal means for said pistons being equally spaced from said centre, means connected to the other end of each piston constraining said piston to move about said centre when the pistons reciprocate in the cylinder, first and second crankshafts for the first and second pistons and each having a crank, means operatively interconnecting said crankshafts for rotation at the same speed, with the throw of the crank of the first crankshaft being phased in advance of the crank of the second crankshaft, and first and second connecting rods each journalled at one end to the crank of the respective crankshaft and at the other eNd to the journal means of the respective piston.
 8. A piston power unit as claimed in claim 7, wherein the means operatively interconnecting said first and second crankshafts comprises intermeshing gears.
 9. A piston power unit as claimed in claim 7, wherein said means operatively interconnecting said first and second crankshafts constrain said crankshafts to rotate in opposite directions. 